EK709
Walls that are constructed before the placement of backfill should be designed to withstand the compaction earth pressures.
EK708
The beneficial effect of passive earth pressures in front of the wallis ignored, because its contribution to resistance is often small for reinforced concrete walls and is only mobilized after […]
EK644
Uplifting failure occurs when there are not enough loads to resist the hydraulic pressure.
EK522
If no drainage is possible from a soil, because the soil has been sealed off, or because the load is applied so quickly and the permeability is so small that […]
EK521
When an assembly of particles in a very loose packing is being loaded by shear stresses, there will be a tendency for volume decrease. This is called contractancy.
EK520
Dilatancy is the increase in volume that may occur during shear.
EK519
As long as the stresses remain below the preconsolidation load the soil is reasonably stiff, but beyond the preconsolidation load the bahavior will be much softer.
EK518
When reloading a soil there is probably less occasion for further sliding of the particles, so that the soil will be much stiffer in reloading than it was in the […]
EK517
Because the deformations of soils are mostly due to changes in the particle assembly, by sliding and rolling of particles, it can be expected that after unloading a soil will […]
EK516
Floatation will happen if the body on the average is lighter than water.
EK515
The upward flow through the clay layer is denoted as seepage.
EK514
In a fluid at rest no shear stresses can be transmitted. This means that the pressure is the same in all directions.
EK513
The pressure in the porewater is denoted as the pore pressure.
EK512
Sand and rock show practically no creep, except at very high stress levels.
EK511
Undrained shear strength is the shear strength of a soil when sheared at constant volume.
EK510
Cohesion is a measure of the resistance due to intermolecular forces.
EK509
Effective friction angle is a measure of the shear strength of soils due to friction.
EK508
The settlement of non-draining soils consists of three parts: Elastic compression (short term; occurs during construction). Primary consolidation (long term; occurs during the design life of the structure). Secondary compression […]
EK507
There are two common modes of settlement of non-free-draining soils (fine-grained soils, fine sand, and medium sand with fines greater than 10%). One is the natural drainage of water from […]
EK506
The settlement of free-draining coarse-grained soils (e.g., medium sand with fines less than 5%, clean, coarse sand) is generally calculated assuming that these soil behave as elastic materials.
EK505
Because of the variability of soils and the complexity of their behavior, it is difficult to estimate settlement unless simplifying assumptions are made. One of these assumptions is that the […]
EK504
Settlement is divided into rigid body or uniform settlement, tilt or distortion, and nonuniform settlement.
EK503
Coarse sand with fines >10%, fine sand and medium sand are not free-draining. Settlement in these soils can occur well beyond the construction period.
EK502
Compaction is the densification of soils by the expulsion of air.
EK501
The time dependent settlement or densification of soils, essentially fine-grained soils, by the expulsion of water from the voids is called consolidation.
EK500
The time rate of settlement of coarse-grained and fine-grained soils is different. Free draining, coarse sand and gravel with fines <5% generally have good drainage qualities (high hydraulic conductivity), so […]
EK499
Overconsolidation ratio (OCR) is the ratio by which the current vertical effective stress in the soil was exceeded in the past.
EK498
Overconsolidated soil is one that has experienced vertical effective stresses greater than its existing vertical effective stress.
EK497
Normally consolidated soil is one that has never experienced vertical effective stresses greater than its current vertical effective stress.
EK496
Excess porewater pressure is the porewater pressure in excess of the current equilibrium porewater pressure.
EK495
Secondary compression is the change in volume of a fine-grained soil caused by the adjustment of the soil internal structure after primary consolidation has been completed.
EK494
Primary consolidation is the change in volume of a fine-grained soil caused by the expulsion of water from the voids and the transfer of stress from the excess porewater pressure […]
EK493
Consolidation is the time-dependent settlement of soils resulting from the expulsion of water from the soil pores.
EK492
Elastic settlement is the settlement of a geosystem that can be recoverable upon unloading.
EK491
Downward seepage increases the resultant effective stress; upward seepage decreases the resultant effective stress.
EK490
Soils, especially silts and fine sands, can be affected by capillary action. Capillary action results in negative porewater pressures (suction) and increases the effective stresses.
EK489
The effective stress in a saturated represents the average stress carried by the soil solids and is the difference between the total stress and the porewater pressure.
EK488
Porewater pressure can be positive or negative.
EK487
Soils cannot sustain tension. Consequently, the effective stress cannot be less than zero.
EK486
The effective stress is the average stress on a plane through the soil mass.
EK485
The porewater cannot sustain shear stresses, and therefore, the soil solids must resist the shear forces.
EK484
The principle of effective stresses applies only to saturated soils.
EK483
The principle of effective stresses applies only to normal stresses and not to shear stresses.
EK482
Deformations of soils are a function of effective stresses, not total stresses.
EK479
Porewater pressure is the pressure of the water held in the soil pores.
EK478
Total stress is the stress carried by the soil particles and the liquids and gases in the voids.
EK477
Effective stress is the stress carried by the soil particles.
EK462
Retaining walls backfilled with cohesionless soils (sand and gravel) tend to rotate slightly around the base. Behind such a wall, a wedge of soil tends to shear along inclined plane. […]
EK461
Passive pressure opposes motion of a structure.
EK460
Active pressure tends to move a structure in the direction in which the pressure acts.
EK459
Batter piles in the center of a pile group are largely ineffective in resisting lateral loads.
EK458
Resistance of pile groups to lateral loads indicate that pile spacings less than about 8 pile diameters in the direction of loading reduce the soil modulus. The reduction factors are […]
EK457
The lateral load capacity of a specific pile type can be most effectively increased by increasing the diameter, i.e., the stiffness and lateral-bearing area. Other steps are to improve the […]
EK456
Vertical pile resistance to lateral loads is a function of both the flexural stiffness of the pile, the stiffness of the bearing soil in the upper 4 diameter to 6 […]
EK455
A point of equilibrium, called the neutral plane, exists where the negative skin friction changes over into positive shaft resistance. This is where there is no relative movement between the […]
EK454
Influenced by consolidation induced by placement of fill and/or lowering of the water table, soils along the upper portion of a pile will tend to compress and move down relative […]
EK453
Piles in clay always yield values of group efficiencies less than unity with a distinctive trend toward block failure in square groups with spacing to diameter or width ratio of […]
EK452
In loose sand, the group efficiency in compression exceeds unity, with the highest values occurring at a pile center to center spacing to diameter or width ratio of 2.
EK451
The efficiency of a pile group is defined as the ratio of the actual capacity of the group to the summation of the capacities of the individual piles in the […]
EK389
The minimum depth for mass concrete foundation is established by 45 degrees dispersal from the edge of the baseplate. Shallower foundations can be used if they are suitably reinforced.
EK309
For dry, granular, noncohesive materials, the assumed linear pressure diagram is fairly satisfactory; cohesive soils or saturated sands behave in a different, nonlinear manner. Therefore, it is very common to […]
EK308
If the retaining wall moves toward the soil, a passive soil pressure develops.
EK307
Under soil pressure, the retaining wall may deflect or move a small amount from the earth, and active soil pressure develops.
EK306
If the retaining wall is assumed absolutely rigid, a case of earth pressure at rest develops.
EK305
If the footing is resting on a cohesive soil such as clay, the pressure under the edges is greater than at the center of the footing.
EK304
The clay near the edges has a strong cohesion with the adjacent clay surrounding the footing, causing the nonuniform pressure distribution.
EK303
The cohesionless soil tends to move from the edges of the footing, causing a reduction in pressure, whereas the pressure increases around the center to satisfy equilibrium conditions.
EK302
Distribution of pressure on cohesionless soil (sand) under a rigid footing.
EK301
The actual distribution of soil pressure is not uniform but depends on many factors, especially the composition of the soil and the degree of flexibility of the footing.
EK51
Vertical pile resistance to lateral loads is a function of both the flexural stiffness of the shaft, the stiffness of the bearing soil in the upper 4D to 6D length […]